In the aviation industry high-performance thermoplastic materials have started to replace metals in many fields. In this paper a novel pipe-extrusion process for high-temperature polyetherimide (PEI) is presented with special emphasis on the calibration and cooling of the pipes. Both the weight advantage over stainless steel pipes and the price advantage over titanium confirm a high potential of thermoplastic pipe systems in the aviation sector. The pipe systems installed in aircrafts are characterised by many variations in terms of geometries (diameter, wall thickness, etc.). The design diversity of thermoplastics can be used to exploit additional potentials in terms of mass savings, production efficiency and cost reduction. In order to address the forecasts of growing aviation transport capacity and aircraft production volume especially the production efficiency will be stronger focused in long term. This paper describes an approach to extrude PEI pipes with variable wall thickness. Special emphasis was laid on the temperature profiles of the pipes inside the calibration system. An approach is presented to measure the cooling behaviour of the extruded pipes online while analysing the wall thickness distribution. Furthermore a subsequent numerical simulation model is presented that seamlessly determines the temperature history of the pipe wall calculating the temperature gradients along and inside the pipes. The results of the simulation and the measurements led to an in-depth understanding of the process parameters needed to extrude PEI pipes with variable wall thickness.